In the case of a wiper lever of the type designated in the pre-characterizing clause of the independent claim, the supporting element of the wiper blade is supposed to guarantee, over the entire wiper field being covered by the wiper blade, the most uniform possible distribution of wiper blade application force on the window originating from the wiper arm. Due to the corresponding curvature of the relaxed supporting element—i.e., when the wiper blade is not adjacent to the window—the ends of the wiper strip that are placed completely against the window during wiper blade operation are loaded by the supporting element that is stressed vis-à-vis the window, even when the radii of curvature of spherically curved vehicle windows change with every wiper blade position. As a result, the curvature of the wiper blade must be somewhat greater than the greatest curvature measured in the wiper field on the to-be-wiped window. The supporting element thereby replaces the expensive supporting bracket design that is required to distribute the application force and that has two spring rails, which are arranged in the wiper strip and are used for transverse reinforcement of the rubber elastic wiper strip, as is the practice with conventional wiper blades (DE-PS 1247 16 1).
In the case of a known wiper lever with a wiper blade where, for reasons related to bearing pressure distribution, the supporting element projects in the wiper blade middle range far beyond the width of the wiper strip (DE-PS 1247161), the front side facing the air stream can be affected by the build-up of excess pressure. On the other hand, a considerable negative pressure builds up on the rear side facing away from the air stream due to the abovementioned wiper blade structure. In operation, though the wiper blade executing a pendulum motion constantly changes its position relative to the inflowing air stream, its one longitudinal side does indeed continually face this stream more or less strongly and is therefore designated as the front side while its other longitudinal side consequently is also viewed as the rear side. In the combined action of these two previously mentioned pressures, both of which are acting in the opposite direction of the wiper blade application force, they are at least reduced at higher travel speeds so that a proper wiper result is no longer possible. In order to remedy this unfavorable flow behavior, in the case of a known wiper lever in accordance with the species (DE 198 56299.3 A1), a wind deflector strip with a flow surface facing one of the main flow directions is arranged on the upper band surface of the supporting element. This wind deflector strip has two sections or partial strips each of which extends from the connecting device to the ends of the supporting element or the wiper blade. As a result, this produces a free space in the progression of the wind deflector strip for positioning the connecting device. Manufacturers of luxury class vehicles in particular object to this optical interruption of the wind deflector strip for reasons related to styling. In addition, this interruption of the flow surface on the wind deflector strip contributes to an undesirable increase in air stream noise due to the edges and gaps that are thereby produced.
It is true that adapting the cross-section of a holder situated in the longitudinal middle area of the wiper blade on its upper band surface for two spring rails belonging to the supporting element to the cross-section of the wind deflector strip sections extending on both sides of the holder is known in the case of the wiper lever according to the species, but the means to connect the wiper blade to the wiper arm are also completely free in this case so that this wiper lever, including a wiper arm and wiper blade, is also encumbered with the already described disadvantages.